Schedule of Debt Outstanding (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011
Schedule Of Debt Instruments [Line Items]
Debt and capital lease obligations	$ 5,903	[1]	$ 4,939	[1]
Current portion	(323)	[1]	(190)	[1]
Long-term portion	5,580	[1]	4,749	[1]
Variable-Rate Loan due 2012
Schedule Of Debt Instruments [Line Items]
Debt and capital lease obligations			180	[1]
One Point Eight Percent Notes Due Two Thousand and Thirteen
Schedule Of Debt Instruments [Line Items]
Debt and capital lease obligations	301	[1]	305	[1]
Effective Interest Rate	2.00%	[2]
Four Point Zero Percent Notes Due Two Thousand and Fourteen
Schedule Of Debt Instruments [Line Items]
Debt and capital lease obligations	358	[1]	365	[1]
Effective Interest Rate	4.20%	[2]
Variable Rate Loan due 2015
Schedule Of Debt Instruments [Line Items]
Debt and capital lease obligations	243	[1]	257	[1]
Effective Interest Rate	0.90%	[2]
Four Point Six Two Five Percent Notes Due Two Thousand and Fifteen
Schedule Of Debt Instruments [Line Items]
Debt and capital lease obligations	646	[1]	667	[1]
Effective Interest Rate	4.80%	[2]
Five Point Nine Percentage Notes Due Two Thousand Sixteen
Schedule Of Debt Instruments [Line Items]
Debt and capital lease obligations	631	[1]	639	[1]
Effective Interest Rate	6.00%	[2]
One Point Eight Five Percent Notes Due Two Thousand and Seventeen
Schedule Of Debt Instruments [Line Items]
Debt and capital lease obligations	500	[1]	499	[1]
Effective Interest Rate	2.00%	[2]
Variable Rate Loans Due Two Thousand Seventeen
Schedule Of Debt Instruments [Line Items]
Debt and capital lease obligations	170	[1]
Effective Interest Rate	0.60%	[2]
Five Point Three Seven Five Percent Notes due Two Thousand and Eighteen Member
Schedule Of Debt Instruments [Line Items]
Debt and capital lease obligations	499	[1]	499	[1]
Effective Interest Rate	5.50%	[2]
Four Point Five Percent Notes Due Two Thousand and Nineteen Member
Schedule Of Debt Instruments [Line Items]
Debt and capital lease obligations	566	[1]	556	[1]
Effective Interest Rate	4.60%	[2]
Four Point Two Five Percent Notes Due Two Thousand and Twenty
Schedule Of Debt Instruments [Line Items]
Debt and capital lease obligations	299	[1]	299	[1]
Effective Interest Rate	4.40%	[2]
Two Point Four Zero Percent Notes Due Two Thousand and Twenty Two
Schedule Of Debt Instruments [Line Items]
Debt and capital lease obligations	697	[1]
Effective Interest Rate	2.30%	[2]
6.625% Debentures due 2028
Schedule Of Debt Instruments [Line Items]
Debt and capital lease obligations	133	[1]	134	[1]
Effective Interest Rate	6.70%	[2]
Six Point Two Five Percent Notes Due Two Thousand and Thirty Seven
Schedule Of Debt Instruments [Line Items]
Debt and capital lease obligations	499	[1]	499	[1]
Effective Interest Rate	6.30%	[2]
3.65% Notes due 2042
Schedule Of Debt Instruments [Line Items]
Debt and capital lease obligations	298	[1]
Effective Interest Rate	3.40%	[2]
Other Debt and Capital Lease Obligations
Schedule Of Debt Instruments [Line Items]
Debt and capital lease obligations	$ 63	[1]	$ 40	[1]

[1] Book values include any discounts, premiums and adjustments related to hedging instruments.

[2] Excludes the effect of any related interest rate swaps.